THIRD REPORT OF THE DIRECTOR I906 I9 



to plot the geology of the mines it has been necessary to prepare a 

 sketch map on a larger scale than any that has been published. 

 The department cooperated in this work with the representatives 

 of a mining company who had purposed making the survey for 

 private use, and was thus able to secure the map at inconsiderable 

 expense and labor. The general facts relating to geology have 

 already been placed on the map, but owing to the lateness of the 

 season, it was found impracticable to complete the investigation. 



The ores of this district are red and specular hematites, with an 

 average iron content ranging from 40 to 65 per cent. A number 

 of mines have been worked at one time or another and their output 

 amounts to a very respectable total. The principal openings lie 

 within an area from ^ mile to a mile or more in width, which be- 

 gins a short distance from Antwerp, Jefferson co., and extends 

 northeasterly into the town of Gouverneur, St Lawrence co., a dis- 

 tance of about 5 miles. The marked linear distribution observable 

 131 the deposits is conditioned by the occurrence of the associated 

 rocks in belts having a northeast-southwest strike. The important 

 geologic formations comprise crystalline limestones, gneiss and 

 thinly foliated schist, all of which have been upturned and probably 

 closely interfolded, and which are capped at times by small areas 

 of Potsdam sandstone with a strong unconformity at the base. 

 Both the schist and limestone, and possibly the gneiss also, belong 

 to a series of Precambric sediments that has been thoroughly meta- 

 morphosed and subjected to erosive influences through a long 

 period previous to the deposition of the sandstone. The schist 

 seems to have had originally the character of a bituminous shale, 

 for it contains much graphite evenly distributed throughout the 

 layers, indicating an organic derivation for the mineral. There is 

 some diversity in the occurrence of the individual ore bodies, though 

 from a general standpoint, and particularly with respect to their 

 origin, they are all closely related. This difference in the 



geologic surroundings is no doubt accountable for the many views 

 that have been expressed by geologists- who have studied them. At 

 some localities where the Potsdam is present, the ores are gathered 

 along the contacts with the underlying limestone or schist, and in 

 such cases there is often apparent a transition phase with gradu- 

 ation upward into the sandstone. This relation has been adduced 

 in support of the theory that the ores are sedimentary, or at least 

 have been derived from the sandstone. The relation is not con- 

 stant, however, for in some mines the bodies of ore occur whollv 



